The present invention concerns a surface treatment technology for semiconductors and, in particular, it relates to a surface treatment method suitable to elimination of damage induced in an insulator film present at the surface of a semiconductor device, as well as an apparatus for practicing such a method.
In the surface treatment of a semiconductor by using high energy particles generated, for example, in plasmas, it has been known that various types of damage are caused in the insulator film of the semiconductor device due to such high energy particles irradiated to the semiconductor. For eliminating such damage, a method of annealing the semiconductor after surface treatment has been adopted.
Damage to the insulator film is mainly caused by holes induced in the insulator film due to various particles irradiated to a specimen for conducting the surface treatment. The various particles means those elementary particles such as ions, neutrals, electrons, photons or mesons. The holes are induced near the surface of the insulator film. When the holes, after thus induced, move through the insulator film and are trapped at or near the interface between the insulator film and the substrate, this causes changes (damage) in the device characteristics of semiconductor such as the threshold voltage shift, dielectric breakdown, decline in life time for minority carriers, etc.
That is, when the holes are trapped at or near the interface, the trapped holes generate near interface states or interface states, or holes trapped at or near the interface are recombined with thermally excited electrons from the substrate to generate photons, which break the bonds of the crystal lattice at or near the interface to newly generate near interface states or interface states. It is considered that the characteristic degradation as described above is caused by such mechanisms. Accordingly, this damage caused by the holes can not be eliminated completely by merely annealing the semiconductor device after the surface treatment.
That is, if the holes induced in the insulator film in the process of the surface treatment are trapped at or near the interface between the insulator film and the substrate, this may cause damage. However, since the conventional surface treatment method and surface treatment apparatus are not adapted to inhibit the holes induced in the insulator film from being trapped at or near the interface between the insulator film and the substrate, it can not be effectively suppress the occurrence of the damage as described above.